Hold-down for shears and the like



Oct. 6, 1936. H. H. ROGERS 92,056,487

HOLD-DOWN FOR SHEARS AND THE LIKE Filed Feb. 15, 1935, 2 Sheets-Sheet 1 LE I "ii" i W" 7 W W 1 Oct. 6, 1936; H. H. ROGERS 2,056,487

HOLD-DOWN FOR SHEARS AND THE LIKE Filed Feb. 15, 1935 2 Sheets-Sheet 2 Patented Oct. 6, 1936 UNITED STATES PATENT OFFICE HOLD-DOWN FOR SHEARS AND THE LIKE Howard H. Rogers, Moline, Ill.

Application February 15, 1935, Serial No. 6,695

6 Claims. (o1. 1c4 52) The invention relates to improvements in holddownsfor machine tools such as shears and the like and has for its primaryobject the provision of an improved arrangement of this character which is of simple construction and highly efliciehtinuse.

Another object of the invention is the provision of an improved construction of the character indicated whichwill operate smoothly, automatically and efficiently notwithstanding inequalities in, or variations of the thickness of the material or accidental interposition of foreign particles.

' Another object of the invention is the provision of improved construction of the character indicated, having special provisiontherein to take care of leakage in the hydraulic portion thereof. Other objects will appear hereinafter.

' The invention consistsin the conditions and arrangements of parts hereinafter described. 2 The invention will be best understood byreference to the accompanying drawings, forming a part of this specification and in which Fig. 1 is a partial front view of a metalshear equipped with a hold-down embodying the invention;

Fig. 2 an enlarged transverse section taken through oneof a plurality of clamping cylinders employed in the'construction;

Fig. 3 a partial longitudinal diagrammatic section of the machine;

T'Fig; 4 a partial longitudinal section of the machine but showing a modified form of construction of the hold-down arrangement; and

Fig; 5 a partial front view corresponding with Fig.4. 5 The embodiment of the invention illustrated in Figs. 1,2, and 3 comprises an ordinary metal shear having the usual frame I0, bed-plate or work support I I, lower shear knife or blade I2, verticalreciprocating shear head I3, and upper inclined reciprocating shear knife or blade I4. These parts are parts'of an ordinary well known metal shear and constitute no part of the present'invention except in so far as the same cooperate with the novel parts to be presently described.

A clamping bar I5 is mounted as indicated for vertical reciprocation in front of the shear head I3 and above the work supporting table Il,'being suspended upon operating links I6, connected as indicated with operating levers I'I carrying cam rollers I8 cooperating with cams I9 on the main operating shaft of the machine. As shown, the cam I9 is provided with an abrupt suddenacting cam lift or surface 2 I, followed by a gradual cam lift or surface 22, which in turn is followed by a lower cylindrical cam surface 23;

The clamping bar I5 .is normally held in elevated position by means of compression springs 24 on suspending rods 25 arranged at each end of the clamping bar as indicated. By this arrangement, as the shaft 20 revolves,the cam surface or lift 2| will cause sudden initial downward movement of the clamping bar I5 followed by a further slow' and gradual downward movement thereof, until the end of the camsurface 22 is reached, whereupon the cam roller I8 runs on to the cam surface 23, thus permitting the springs 24 to elevate clamping bar I5, as will be readily understood by those skilled in this art.

Arranged on the bottom of the clamping bar I5 is a plurality of oil-filled clamping cylinders 26, each equipped with a piston 2'! carrying a piston rod 28, having a contact head or block 29 at its lower end adapted and arranged to contact with the'upper surface of work on the work table I I. Each piston 21 is normally pressed toward its lowermost position'by means of a light'spring 30 imprisoned as shown in the corresponding cylinder 26. The different cylinders 26 are connected with each other by means of 'an oil-filled pipe 3| leading therefrom to a valve head 32'arranged as shown in Fig. 3 in the bottom of an oil reservoir 33, the pipe 3| being in open communication with oil passage 34 in said valve head. Escape of oil from the passage 34 is controlled by a valve plug 35 normally and adjustably held in sealing position by means of a. heavy compression spring 36, adjustable through a stem 31 by means of a hand wheel 38, as will be readily understood. The escape of oil from the passage 34 is effected through passage '39 when the plug 35 is lifted. A spring-held check valve 40"'controls passage ways'4I and 42 through which oil may enter the passageway 34 when said check valve is open.

The cams I9 are set on the shaft 20 to cause initial sudden mechanical downward movement of the clamping bar I5 just 'prior to the downward stroke of the shear blade or knife I4. This initial movement of the bar I5 quickly brings the clamping heads or blocks 29 into contact with the work on the work table I I prior to the operation of the shear blade I 4, thereby serving to hold the work stationary during the shearing action. The arrangement is such that on this initial contact of the contact heads 29 with the work, the pistons 21 yield upwardly in the cylinders 26, and when sufiicient hydraulic pressure is thus caused in the hydraulic system, the valve plug 25 will raise, permitting escape of oil'and relief of such pressure. Should there be inequalities in the thickness of the material or should foreign particles be accidentally interposed, the different contact heads 29 are free to yield to correspond, but always maintain uniform pressure on the work at the different points of contact. It is also to be noted that the plug valve 35 must move upwardly a material distance before there is any relief of pressure so that said valve thus serves in effect as an accumulator and provides elasticity to the hydraulic system.

During the downward stroke of the shear blade H, the clamping bar l5 will also be forced slowly and gradually downwardly, thereby insuring the maintenance of the uniform holding pressure on the work, notwithstanding any leakage or air traps in the hydraulic system. As soon as the downward cutting stroke of the shear blade- I 4 I is completed, the clamping bar I5 is quickly raised by the action of the springs 24 and the pistons 21 return to normal position. During such return of said pistons, oil is drawn into the cylinders 26 through the'check valve 40 which automatically opens for the purpose, thereby always. maintaining the hydraulic system completely filled with oil and thus insuring proper and uniform action thereof. By this arrangement proper and uniform pressure will always be maintained at the points of application on the work notwithstanding any inequalities in thickness or accidental interposition of foreign particles.

If desired, air pressure may be maintained in reservoir 33, thus accelerating the return of oil to the system when the check valve 40 opens.

In the modified construction illustrated in Figs. 4 and 5, bosses 43 are formed on the front face of the shear head l3 and elongated clamping cylinders 26' secured as shown to the bottoms of these bosses. These clamping cylinders 26 are provided with elongated piston rods 28, having contact heads 29 at their bottom positions, as shown in advance of the lower cutting edge of the shear blade I4. Otherwise the construction is the same as that already described.

By this arrangement, the force and movement for theclamping action is provided by the shear head I3, thus dispensing with the necessity for the use of the clamping bar 15 and its actuating parts. By arranging the contact heads 29in advance of the shear blade 14, said heads come into contact with the work before the shearing action begins, the piston rods 28' yielding upwardly into the cylinders 26' during the shearing action, as will be readily understood. During such upward yielding, the confined oil will escape into the reservoir 33 asbefore, thereby relievingexcessive pressure and maintaining the holding pressure substantially constant. Upon elevation of the shear head l3, the contact heads 29 will be withdrawn from contact: with the work when the shear head reaches the upper end of its stroke. By this arrangement, a construction is provided which is very simple and, therefore, capable of economic production and will operate satisfactorily, particularly on comparatively heavy work.

While I have illustrated and described the preferred forms of construction for carrying my invention into effect, these arecapable of variations and modification without departing from the spirit of the invention. I, therefore, do not wish to be limited to the precise details disclosed; but desire to avail myself of such variations and modifications as fall within the scope of the appended claims.

I claim:

1. In a clamp for holding work to be operated upon by a tool, a frame; a work support on the frame; a tool and means for applying the same to work on said support; a plurality of separate pressure chambers mounted on the tool applying means and each having a spring held piston carrying a piston rod arranged to contact with work on said support, the length of said piston rod and the extent of the movement of said tool applying means being such as to generate automatically sufficient pressure in said chambers to hold said work; a relief reservoir; a pipe connection between said pressure chambers and said reservoir; a relief valve controlling said connection and arranged to yield under excessive pressure; and a check Valve in said connection arranged to' admit liquid from said reservoir to said pipe connection upon decrease of pressure therem.

2. Inna clamp for holding work to be operated upon by a tool, a frame; a work support on the frame; a tool and means for applying the same to work on said support; a reciprocatory member arranged to approachand recede from work on said support; a hydraulic pressure chamber mounted on said reciprocatory member and provided with a yielding piston carrying a piston rod arranged to contact with and hold said work during operation'of said tool, the length of said piston rod and the extent of the movement of said reciprocatory member being such as to generate automatically suflicient pressure in said chambers to' hold said work; and a hydraulic pressure relief system connected with said chamber and arranged to relieve and thereby maintain pressure in said chamber substantially constant. 3. In a clamp for holding work to be operated upon by a tool, a frame; a work support on the frame; .a tool and means for applying the same to the work on said support; a reciprocatory member separate from the tool'applying means arranged to approach .and recede from work on said support; a plurality of hydraulic pressure chambers mounted on said reciprocatory member and each provided'with 'a yielding piston carrying a piston rodarranged to contact with and hold said work during operation of said tool, the length of said piston rod and the extent of the movement of said reciprocatory member being such as to generate automatically sufficient pressure in said chambers to hold said work; and a hydraulic pressure relief system connected with said chambers and arranged to relieve and thereby maintain pressure in said chambers substantially constant.

4. Ina clamp for holding work to be operated upon by a tool, a frame; a work support on the frame; a tool and means for applying the same to work on said support; a reciprocatory member arranged to approach and recede from work on said support; a hydraulic pressure chamber mounted on said reciprocatory member and provided with a yielding piston carrying a piston rod arranged to contact with and hold said work during operation of said tool, the length of said piston rod and the extent of the movement of said reciprocatory member being such as to generate automaticallysufficient pressure in said chambers to hold said work; a relief reservoir; a hydraulic pipe connecting said reservoir and chamber, said chamber, pipe and reservoir containing liquid; a relief valve for said pipe within said reservoir; and a check valve admitting liquid from said reservoir to said pipe upon decrease of pressure in said pipe below that in said reservoir.

5. In a clamp for holding work to be operated upon by a tool, a frame; a work support on the frame; a tool and means for applying the same to the work on said support; a reciprocatory member separate from the tool applying means arranged to approach and recede from work on said support; a plurality of hydraulic pressure chambers mounted on said reciprocatory member and each provided with a yielding piston carrying a piston rod arranged to contact with and hold said work during operation of said tool, the length of said piston rod and the extent of the movement of said reciprocatory member being such as to generate automatically suflicient pressure in said chambers to hold said works; a relief reservoir; a hydraulic pipe connecting said reservoir and chambers, said chambers, pipe and reservoir containing liquid; a relief valve for said pipe within said reservoir; and a check valve admitting liquid from said reservoir to said pipe upon decrease of pressure in said pipe below .that in said I'BSEIVOII.

6. In a clamp for holding work to be operated upon by a tool, a frame; a work support on the frame; a tool and means for applying the same to the work on said support; a reciprocatory member separate from the tool applying means arranged to approach and recede from work on said support; a plurality of hydraulic pressure chambers mounted on said reciprocatory member and each provided with a yielding piston carrying a piston rod arranged to contact with and hold said work during operation of said tool, the length of said piston rod and the extent of the movement of said reciprocatory member being such as to generate automatically suflicient pressure in said chambers to hold said works; a relief reservoir under pressure; a hydraulic pipe connecting said reservoir and chambers, said chambers, pipe and reservoir containing liquid; an adjustable spring held relief valve for said pipe within said reservoir; and a check valve admitting liquid from said reservoir to said pipe upon decrease of pressure in said pipe below that in said reservoir.

HOWARD H. ROGERS. 

